Magnetic logical device



March 18, 1969 o. J. MORRIS MAGNETIC LOGICAL DEVICE Filed Aug. 6, 1964 31,497/63 US. Cl. 307-88 Claims Int. Cl. H03k 17/80 ABSTRACT OF THE DISCLOSURE This invention relates to a magnetic logic device comprising a core having a central aperture and three outer apertures equally spaced around it. Three outer legs between the outer apertures and the periphery of the core and the three inner legs between the outer apertures and the central aperture are all of equal size, and the legs between adjacent outer apertures are at least twice this size. A reset winding is coupled to the outer legs to magnetise the first in one direction and the second and third in the opposite direction. The input windings are coupled to the second and third outer legs so that their magnetisation can be reversed by input signals. An output winding coupled to the first inner leg performs the AND function, the output being generated when a prime winding (coupled to the inner leg) is energised. A further output winding is coupled to the second and third inner legs and performs the EXCLUSIVE OR function, the output being generated simultaneously with the input signals.

The invention relates to magnetic logical devices for storing and producing logical functions of input data.

According to the invention such a device includes an annulus of a magnetic material having an approximately rectangular hysteresis loop, the inner perimeter of the annulus defining a minor aperture and the annulus having three major apertures which have substantially equal perimeters greater than the inner perimeter of the annulus and which are disposed at substantially equal intervals around the annulus, their perimeters defining three inner and three outer parts of substantially equal minimum radial cross-sectional area with the inner and outer perimeters respectively, and between the major apertures, three intermediate parts of which the minimum cross-sectional area of each is at least twice the minimum cross-sectional area of the inner or outer parts, a reset winding around each outer part for receiving reset pulses elfective to reset a magnetic condition of the annulus, around each of two of the outer parts at least one input winding for receiving input signals, and output winding means associated with at least one of the inner parts for producing output signals representing predetermined logical functions of the input signal applied to the input windings.

According to a feature of the invention the annulus has a first input winding around a first outer part associated with a first aperture, a second input winding around a second outer part associated with a second aperture, the first and second outer parts being the said two of the outer parts, and output winding means associated with the inner part between a third aperture and the minor aperture for producing output signals representing a logical AND- function of the input signals applied to the input windings.

According to another feature of the present invention the annulus has a prime winding around at least one of the inner parts effective on energisation to reverse a flux acting round the minor aperture and provide thereby eifective electrical isolation of the output winding means from input signals.

l t United States Patent 0 3,433,973 Patented Mar. 18, 1969 "Ice According to another feature of the present invention the device may be arranged to provide EXCLUSIVE-OR and other logical functions.

According to another feature of the present invention the device may be arranged as a HALF-ADDER.

By way of example two magnetic logical devices according to the invention will now be described with reference to the accompanying drawing in which:

FIG. 1 shows diagrammatically a wire only connected magnetic device for producing the AND functions; and

FIG. 2 shows diagrammatically a HALF-ADDER.

Referring to FIG. 1, an annulus 10 of ferrite material having an approximately rectangular hysteresis loop has a central minor aperture 11 and three major apertures 12, 13 and 14. Three inner parts 15, 16 and 17 of equal radial cross-sectional area separate the minor aperture from the three major apertures. Three outer parts 18, 19 and 20 of equal radial crosssectional area equal to those of the inner parts separate the major apertures from the outer perimeter of the annulus. A reset winding 21 is wound round the three outer parts 18, 19 and 20 so that a reset pulse in the winding will tend to set up fluxes acting around apertures 12 and 13 in counter clock-wise directions and a flux acting around aperture 14 in a clock-wise direction. A prime winding 22 is wound around the inner parts 15, 16 and 17 so that when energized with a limited unidirectional priming current it tends to set up a flux acting around the minor aperture 11 in a counter clockwise direction. An output winding 23 connected by low impedance wire to an input portion of a succeeding magnetic logical device 23A is wound round the inner part 17, and two input windings 24 and 25, connected respectively by low impedance wire to input circuits of preceding magnetic logical devices 24A and 25A, are wound round the outer parts 18 and 19 respectively.

In operation, a pulse in the reset winding 21 sets up a flux pattern in which the flux in parts 15 and 16 are clockwise with respect to aperture 11 while the flux in part 17 is counter clock-wise. The priming current applied to the prime winding 22 cannot reverse the flux direction around the aperture 11 in this condition. An input signal applied to input winding 24 will reverse the flux direction around aperture 12 whilst an input pulse applied to input winding 25 will reverse the flux direction around aperture 13. If input signals are applied to both windings 24 and 25 so that the flux direction around apertures 12 and 13 is simultaneously clock-wise then the field caused by the priming current in the prime winding 22 is able to cause the flux to act round aperture 11 to be in a clock-wise direction. On the occurrence of the next reset pulse the flux in part 17 will be reversed and an output signal will be induced in output winding 23. If however, one of the input windings 24 and 25 does not receive an input pulse the priming current cannot cause the flux to act round aperture 11 in a clock-wise direction so that on the occurrence of a subsequent reset pulse no reversal of flux in part 17 occurs so that no output signal is induced in the winding 23. An output signal in the output winding 23 may occur only when there is an input signal to windings 24 and 25 simultaneously so that the output signal repre sents a logical AND-function of the input signals.

The change of flux direction caused by the input signals is isolated from the output part 17 of the device and only transferred by action of the priming current. The output winding 23 can be in a low impedance circuit such as in the wire only scheme described using multiaperture cores as shown in the drawing. Preferably, in such a scheme a hold winding is wound on part 17 which sets up a field acting in a clockwise direction around the aperture 14 when the multi-aperture core linked with the output winding 23 is reset; this hold field prevents the back fiow of data from the succeeding magnetic logical circuits during resetting. Another way in which back flow of data can be prevented in the low impedance output circuit is to isolate the flux change set in an input aperture of the following multi-aperture device using a second prime winding linked with that aperture.

Referring to FIG. 2, the HALF-ADDER is similar to the device shown in FIG. 1 as indicated by reference lettering; the HALF-ADDER has no prime winding. A further output winding 26 is wound in series round the inner parts 15 and 16. The input and output windings are respectively associated with controllable impedance amplifier devices 23B, 24B, 25B and 26B.

In operation, a reset pulse sets up a flux acting around aperture 14 in a clock-wise direction and a flux acting around apertures 12 and 13 in a counter clock-wise direction. An input signal applied to input winding 24 causes the flux to reverse around aperture 12 and an input signal to the input winding 25 causes the flux to reverse around aperture 13. If input signals are applied simultaneously so that the flux round outer circumferences of apertures 12 and 13 becomes simultaneously clock-wise a reverse in direction of the flux in part 17 is effected.

If the input signal to input Winding 24 is defined as A and the input signal to input winding 25 is defined as B then the output signal at output winding 26 may be defined as A'EA-ZB, producing an EXCLUSIVE-OR function of the input signals A and B, and the output signal at output winding 23 may be defined as AB, producing the AND-function of the input signals A and B. The combination of these output signals gives the requirements of a HALF-ADDER device; AF-i-ZB providing the SUM- function and AB providing the CARRY function.

While the particular all-magnetic example has described a HALF-ADDER it is possible to produce other functions; for example by using combinations of input windings around parts 18 and 19 the output signal can be made to depend upon more than two variables. For example, a device for producing an AND-function having input signals represented by A and B will produce an output signal in output winding 23 whenever signals A and B are present simultaneously. If now a winding is added to receive input signals C which acts to assist input signals A, the device will produce an output signal in output winding 23 whenever signal A or C is present simultaneously with signal B. Alternatively, if input signal C is arranged to oppose input signal A, the device will produce the output signal whenever signals A and B are present simultaneously provided signal C is not present.

Non-destructive read-out of the data in the device may be achieved by energizing the prime winding 22 with an alternating current, of limited amplitude, instead of with a unidirectional current pulse, thus inducing in the output winding 23 an alternating signal in accordance with input signals being presented to both the input windings 24 and 25.

In general, the signals for the devices are of such a predetermined magnitude that they may eifect only a shortest flux path associated with their respective windings. Whenever an input signal is present for operation it has this predetermined magnitude. Output signals may be detected at output windings during resetting of the device, that is, at the instant of application of a reset pulse to the reset winding or, alternative output signals may be detected during a setting condition, that is, at the instant two input signals are applied simultaneously at input windings. In short, output signals may be detected whenever the direction of the flux associated with an output winding is changed. In systems incorporating controllable impedance amplifier devices the input and output signals are not isolated from one another for operation.

In all-magnetic systems, or wire-only connected" systerns, a prime winding is necessary which is effective on energisation, by a unidirectional priming current or a priming pulse, to tend to reverse associated flux directions around an aperture. In these circumstances an output signal may be detected, if desired, at the output windings whenever the prime winding actually reverses such a flux. Introdutcion of a prime winding effects a reversal of the polarity of output signals withrespect to input signals and electrical isolation of input circuits from output circuits.

What I claim as my invention and desire to secure by Letters Patent is:

1. A magnetic logic device comprising:

a saturable magnetic element having a central aperture and at least three outer apertures arranged symmetrically around the central aperture, thereby defining outer anms between the outer apertures and the circumference of the element and corresponding inner arms between the outer apertures and the inner aperture, all said arms being of substantially equal size and the arms between adjacent outer apertures being at least twice that size;

reset means for initially magnetising one of the outer arms in one direction and all other outer arms in one direction and all other outer arms in the opposite direction;

individual input means coupled to each of said other outer arms for reversing their magnetisation in response to respective input signals;

and output means for detecting a change of magnetisation in the inner arm corresponding to said one outer arm.

2. A magnetic logic device according to claim 1 and including prime means coupled to the inner arms for reversing the magnetisation of the inner arms provided that all the inner arms are magnetised in the same direction.

3. A magnetic logic device comprising:

a saturable magnetic element having a central aperture and first, second and third outer apertures arranged symmetrically around the central aperture, thereby defining first, second and third outer arms between the respective outer apertures and the circumference of the element and first, second and third inner arms between the respective outer apertures and the inner aperture, all said arms being of substantially equal size, and the arms between adjacent outer apertures being at least twice that size;

reset means for initially magnetising the first outer arm in one direction and the second and third outer arms in the opposite direction;

individual input means coupled to the second and third outer arms for reversing their magnetisation in response to respective input signals;

and EXCLUSIVE-OR output means for detecting a change of magnetisation in the second and third inner arms.

4. A magnetic logic device according to claim 3 and including prime means coupled to the inner arms for reversing the magnetisation of the inner arms provided that all the inner arms are magnetised in the same direction.

5. A magnetic logic device according to claim 4 and including AND output means for detecting a change of magnetisation in the first inner arm.

References Cited UNITED STATES PATENTS 2,919,430 12/1959 Rajchman 340-174 JAMES W. MOFFITT, Primary Examiner.

US. Cl. X.R. 

